This application relates to imaging systems, and in particular to a panoramic camera system that provides a high precision extended field of view.
The usefulness and popularity of imaging systems have steadily grown in the wake of technological advances in image processing and material design. A panoramic camera is one type of imaging system that collects a panoramic view of a scene in a single snap shot Panoramic cameras have use in surveillance, video conferencing, automotive, and machine vision technologies. Moreover, consumer panoramic photography is becoming a popular form of artistic expression.
To address the growing need for such imaging systems, many panoramic image capture systems have evolved. Although these different technologies provide for panoramic image capture, they do so at the expense of accuracy, clarity, and cost.
For instance, Canadian patent no. CA2335657A1 and international publication no. WO2006/093387A1 disclose panoramic systems that collect images using multiple cameras positioned in different locations. Unfortunately, the multiple cameras increase the complexity and cost of the imaging systems, thus rendering them unfeasible for most applications. Compounding this problem, some imaging systems have been designed that employ multiple reflective mirrors and cameras to collect panoramic images. U.S. Pat. Nos. 5,539,483 and 6,560,413, and U.S. published patent applications US2005/0117015 and US2006/0023106 disclose these types of systems. Because these systems use multiple cameras in connection with multiple mirrors, the complexity and cost of their design make them unattractive options for consumer applications. Moreover, these types of imaging systems are unable to capture images from the top side of the system.
Other imaging systems have been designed that provide panoramic views without using multiple cameras. For example, FIG. 1 shows a conventional fisheye type panorama camera that uses multiple lenses to direct images to a receiving area. However, because less information and Modular Transfer Function (MTF) are allocated to the border areas of the lenses, which provide the more distant scenes of a captured image, the fisheye camera produces distorted images. And while implementing high resolution image sensors may reduce the distortion effects produced by the lenses, such implementations would increase the cost of the system rendering it less feasible option for most applications.
Additional imaging systems implement mirrors aligned to an image capture device. U.S. published patent application US 2005/0013022 and Great Britain patent no. GB2423156 disclose such designs. These types of systems use a single curvilinear mirror aligned to an image capture device. However, these systems also produce distorted images because less information and worse MTF are allocated to a center area that is reserved for capturing information for near scenes. Moreover, these designs produce a blind spot where the mirror is fixed to the system. Similar to the fisheye design, higher resolution image sensors may be employed to reduce the distortion caused by the design, but such implementations would increase the cost of the system.
A variation to the single curvilinear mirror design is shown in international publication no. WO2004051340 and U.S. Pat. No. 6,175,454. These designs include a panorama camera system that uses multiple curvilinear mirrors and lenses aligned to an image capture device. Unfortunately, as with other conventional mirror designs, these systems also produce distorted images because less information is allocated to a center area that maintains information for far scenes of a captured image. Further, these multiple curvilinear designs also fail to capture scenes from the top side of the system. Also, while higher resolution image sensors may be employed to reduce the distortion caused by the design, such implementations would increase the cost of the system.
To address the top side view deficiencies of the above described multiple curvilinear mirror designs, panorama camera systems have been designed to include multiple curvilinear mirrors and lenses at the top side of the systems. International publication no. WO2005106543 describes such a system. And though this design may provide wider fields of view than single camera designs, the image generated has discrete distortion between, and at, the center and borders of the image. Moreover, the image processing that is required to compensate for the distortion and to stitch the top and side views together may be difficult to implement.
Other forms of panorama camera systems include Japanese patent no. JP2007101662 that discloses a panorama camera system using a rolling iris, lens set, curved shape image sensor, a mechanical control unit, and an image processing unit. The rolling iris scans the scene and the image sensor captures stripes of the collected images to produce a panoramic view of the scene. However, the mechanical parts necessary to perform the image capture disclosed in this patent increase the cost and decrease reliability of the system. Moreover, it may be difficult to mass produce the curved shaped image sensor using main stream semiconductor technologies.
Accordingly, there is a need for a low cost panoramic camera design that is more robust and stable, has a wider view angle, provides a smaller form factor, and provides less distortion than conventional panoramic camera systems.